1. Field of the Invention
The present invention relates to aqueous or aqueous solvent containing disinfectant solutions having improved corrosion properties.
2. Description of Related Art
Immediately after use, medical instruments are placed in an aqueous solution of disinfectants for cleaning and disinfection. The resulting destruction of vegetative germs and spores depends on the concentration and contact time of the disinfectant solution.
Commercially available disinfectant solutions contain as antimicrobial agents, inter alia, phenol derivatives, active chlorine donors, quaternary ammonium compounds or aldehydes or mixtures of these agents, preferably mixtures of quaternary ammonium compounds and aldehydes of the type known, for example, from German Application No. 26 11 957. While these agents are performing their disinfecting functions, however, the treated surfaces, especially the surfaces of instruments and appliances, have to be protected against corrosive attack. Accordingly, it is important to prevent corrosion by disinfectants without impairing the level of disinfection.
German Pat. No. 2,141,982 relates to disinfectants having a particularly strong cleaning and disinfecting effect comprising a combination of quaternary ammonium compounds and phosphonocarboxylic acids, such as 2-phosphonobutane-1,2,4-tricarboxylic acid and salts thereof, the latter acting as sequestrants. However, it is known, for example from Roempps Chemie-Lexikon, 7th Edition (1974), page 2644, that 2-phosphonobutane-1,2,4-tricarboxylic acid is also a basic ingredient of corrosion inhibitors.
This is also apparent from Japanese Patent Application No. 76/6831, according to which, inter alia, nitrilotriacetic acid and ethylene diamine tetracetic acid can also be added.
Accordingly, 2-phosphonobutane-1,2,4-tricarboxylic acid was added to known commercial disinfectants based on aldehydes and quaternary ammonium compounds in order thus to avoid any corrosive effects. However, it was found that this reduced the pH-value of disinfectant preparations to below pH 3.0, producing a serious deterioration in their stability. This could be prevented by adding sodium hydroxide and adjusting the pH-value to 3.5-4.0. However, even at higher pH-values, there was a deterioration in the stability of the prepared solutions.
Other sequestrants, such as salts of aminopolycarboxylic acids, also produced marked improvements in the corrosion behavior of disinfectants, provided the pH-value of the concentrate was reduced to pH 3.5-4.0 by addition of acids, for example formic acid, for reasons of stability.